Ceramic capacitor and methods of manufacture

ABSTRACT

A capacitor includes a pair of electrodes and a metalized dielectric layer disposed between the pair of electrodes, in which the metalized dielectric layer has a plurality of metal aggregates distributed within a dielectric material. The distribution is such that a volume fraction of metal in the metalized dielectric layer is at least about 30%. Meanwhile, the plurality of metal aggregates are separated from one another by the dielectric material. A method for forming a metal-dielectric composite may include coating a plurality of dielectric particles with a metal to form a plurality of metal-coated dielectric particles and sintering the plurality of metal-coated dielectric particles at a temperature of at least about 750° C. to about 950° C. to transform the metal coatings into discrete, separated metal aggregates. Contrary to conventional techniques of separating electrodes by a dielectric tape, this inventive system and method demonstrates that a metalized dielectric layer may be formed in-situ during sintering.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority under35 U.S.C. § 120 to U.S. non-provisional application entitled “CAPACITORWITH THREE-DIMENSIONAL HIGH SURFACE AREA ELECTRODE AND METHODS OFMANUFACTURE,” filed on Dec. 15, 2010 assigned application Ser. No.12/969,186. Priority under 35 U.S.C. § 119(e) is also claimed to U.S.provisional application entitled “CERAMIC CAPACITOR AND METHOD OF MAKINGTHE SAME,” filed on Oct. 12, 2010 assigned application Ser. No.61/392,450. The entire contents of these two patent applications arehereby incorporated by reference.

BACKGROUND

A capacitor is any device having the principal electric property ofcapacitance, i.e. the ability to store an electric charge. In the fieldof electronics, the ability of a capacitor to store an electric chargeis useful in controlling the flow of an electric current. Moreover,capacitors may be employed in circuits for the purpose of filteringelectrical signals; for example, a capacitor with variable capacitancecan be used in the tuning circuit of a radio or television receiver.Varying the capacitance changes the resonant frequency of the tunercircuit so that it matches the frequency of the desired station orchannel, filtering out signals of all unwanted frequencies.

The simplest of capacitors will comprise two plates of a conductivematerial separated from one another by an insulator, also referred to asa dielectric, with each plate connected to a terminal. When voltage isplaced across the terminals of an uncharged capacitor, charge flows toeach of the plates (positive charge to the anode plate and negativecharge to the cathode plate) but not across the insulator sandwichedbetween the conductive plate. As the opposite charges increase on theconductive anode and cathode plates, the force on the dielectric betweenthem also increases, thereby causing the electric field across thedielectric to increase. This phenomenon gives rise to a voltage whichincreases proportionally with the charge on the plates.

The ratio of the charge magnitude on each plate to the electricpotential (voltage) between the plates is the aforementioned capacitanceand approximates the externally applied voltage source used to chargethe capacitor. When these two voltages have the same magnitude (thevoltage source and the capacitor), the current ceases to flow and thecapacitor is considered to be charged. A charged capacitor issubsequently discharged by reducing the external voltage through anapplied electrical load, thus causing a decrease in the voltage acrossthe plates when a produced current quickly flows the charge off theplates.

There are many types of capacitors, each varying in construction andmaterial combinations, but the physics explained above are essentiallythe same for all. A common capacitor type employs ceramic for thedielectric layer and may take either a cylindrical structure, wherein ahollow cylinder of the ceramic material is lined with thin films ofconductive metal on its inner and outer surfaces, or a flat, parallelplate structure wherein a plurality of plates of ceramic and conductivematerials are interleaved to create the sandwiched“electrode-dielectric-electrode” arrangement.

Manufacturing is fairly straightforward for capacitors comprising of theso-called parallel plate structure. A layer of dielectric is sandwichedbetween two conductive electrode layers, wherein capacitance of theresulting parallel plate capacitor is a function of the overlapped areaof the electrode plates, thickness of the dielectric layer, and thepermittivity of the dielectric.

A multi-layer ceramic capacitor (MLCC) is a parallel plate capacitorhaving a plurality of stacked “electrode-dielectric-electrode”arrangements (EDE), where each may form a tri-layer. The capacitance ofa MLCC may be drastically increased by the parallel connection of themany parallel plates. Quite simply, more stacked arrangements increasescapacitance and forms a MLCC. Similarly, individual capacitors can alsobe connected in series, essentially spreading the above described MLCCover a larger surface area as opposed to a higher amount of head room.

An advantage of serially connected capacitors over a highly stacked MLCCis that the serial arrangement is known in the art to exhibit betterresistance to voltage breakdown (as the charge and voltage on a givencapacitor are increased, at some point the dielectric will no longer beable to insulate the charges from each other, subsequently exhibitingdielectric breakdown, or high conductivity in some areas, which tends tolower the stored energy and charge, generating internal heat).

Turning back to the manufacturing methods employed to make typicalMLCCs, a capacitor may be made by applying a dielectric slurry, such asa ceramic based slurry, between alternating pairs of conductive plates.However, the manufacturing of MLCCs has largely migrated to the use of aconductive ink or paste (an ink or paste comprising a conductivematerial such as, for example, silver), in lieu of plates; This ink orpaste may be screen-printed over a “green tape” of a dielectric slurrywhich was previously cast on a carrier polymer film. Consistent withwhat has been described above, many layers of interleaved dielectrictapes and electrode applications can be stacked and laminated togetherto form a final MLCC product.

Multi-layer ceramic capacitors with about 500 to about 1000 layers,where the dielectric layers often being less than about 1 micronthickness, are achievable. Reduction in layer thickness in a MLCCdirectly correlates with saved head room, however, it is often not theheadroom that comes at a premium. In actuality, the overall surface arearequired to accommodate a passive electrical component, such as a MLCC,represents valuable real estate in an electrical circuit.

To reduce the space passive components occupy using surface mounttechnology, 0402 size (about 0.04 inch by about 0.02 inch) is gainingmomentum as the most popular and even 0201 (about 0.02 inch by about0.01 inch) can be reliably produced. Generally, when holding capacitanceconstant, the smaller the MLCC is, the better. However, there is a limitto simply reducing the area footprint and increasing layer quantities ascontinued reduction in the thickness of dielectric and electrode layerscan create manufacturing problems. Therefore, there is a need to providealternate methods to continue the trend to reduce the size and increasethe capacitive density of the ceramic capacitor, and there is a need forcapacitors exhibiting enhanced capacitive density.

SUMMARY

In one aspect, a capacitor is disclosed that includes a pair ofelectrodes and a metalized dielectric layer disposed between the pair ofelectrodes, in which the metalized dielectric layer has a plurality ofmetal aggregates distributed within a dielectric material. Thedistribution is such that a volume fraction of metal in the metalizeddielectric layer is at least about 20 weight percent (wt %), or at leastabout 30 wt %, or at least about 40 wt %, or at least about 50 wt %,e.g., in a range of about 30 wt % to about 60 wt %. In many embodiments,the plurality of metal aggregates (also referred to as “metalinclusions”) are separated from one another by the dielectric material.

In many embodiments, the metal aggregates provide a significant volumefraction of the metalized dielectric layer, such as the above volumefractions, without forming a percolation metal network.

In some exemplary embodiments, the volume fraction of the metal in themetalized dielectric layer may be greater than about 40%, e.g., in arange of about 40% to about 60%. In other embodiments, the volumefraction of the metal may be in a range of about 50% to about 60%.

In some embodiments, the metalized dielectric layer can have a thicknessin a range of about 0.01 to about 250.0 microns.

In some embodiments, the metalized dielectric layer is separated from atleast one of the electrodes by a substantially metal free dielectriclayer (herein also referred to as “depletion layer”). In some suchembodiments, the metalized dielectric layer is separated from each oftwo electrodes between which it is disposed by a substantially metalfree dielectric layer. In some embodiments, the thickness of thesubstantially metal free dielectric layer is in a range of about 5.0 toabout 10.0 microns.

In some embodiments, the metalized dielectric layer is configured as afloating electrode (i.e., an electrode that is not configured forcoupling to an external voltage source), while in some otherembodiments, the metalized dielectric layer is configured as anelectrode suitable for electrical coupling with a voltage terminal.

In some embodiments, the above capacitor having the metalized dielectriclayer exhibits a capacitance that is at least 2 times (e.g., in a rangeof 2 to about 1000 times) greater than the capacitance of a putativecapacitor having the same size, electrodes, and dielectric material butlacking the metal inclusions.

In some embodiments, the dielectric material comprises a ceramic. Forexample, the dielectric material can be in the form of a plurality ofceramic particles having a size, e.g., in a range of about 0.01 micronsto about 15.0 microns, and more particularly from about 0.05 microns toabout 10.0 microns. In many such embodiments, the metal aggregates ofthe metalized dielectric layer can be in the form of metal inclusiondisposed on the outer surfaces of the ceramic particles.

In some embodiments, the ceramic particles are formed of any of BaTiO3,doped BaTiO3, and other barium titanates dielectrics.

In some embodiments, in the above capacitor, at least one of theelectrodes is formed of a metallic constituent that has at least onecomponent in common with the metal incorporated in the dielectric. Forexample, in some embodiments, both electrodes are formed of the samemetal as that incorporated in the dielectric.

In another aspect, a capacitor is disclosed that includes at least onepair of electrodes and a dielectric layer disposed between theelectrodes, where the dielectric layer includes a metalized portion. Themetalized portion can be in the form of a metal-dielectric composite inwhich separated metal inclusions are distributed within the dielectric.The capacitor exhibits a capacitance that is at least about 3 times, orat least about 5 times, or at least about 10 times, or at least about 20times greater than the capacitance of a control capacitance that isidentical in every respect (e.g., it has the same size with electrodesand the dielectric layer formed of the same metal and dielectricmaterial, respectively) except for lacking the metal incorporated in thedielectric layer. For example, the capacitor can exhibit a capacitancethat is greater than that of the control capacitor by a factor in arange of about 3 to about 1000.

In some embodiments, an effective dielectric constant of themetal-incorporated dielectric can be in range of about 20 to about 120for a normal dielectric with a dielectric constant of 20. While in someembodiments, the metal inclusions are distributed throughout the entiredielectric layer in other embodiments the metal inclusions are confinedwith a portion of the dielectric layer. In some cases, such a metalizedlayer can be separated from at least one of the electrodes by a layerthat is substantially free of the metal inclusions (“depletion layer”).

In another aspect, a method for forming a metal-dielectric composite isdisclosed that may include coating a plurality of dielectric particleswith a metal to form a plurality of metal-coated dielectric particlesand sintering the plurality of metal-coated dielectric particles totransform the metal coatings into a plurality of discrete, separatedmetal aggregates. In general, the sintering temperature is selectedbased on the metal used for coating the ceramic particles. For example,in some embodiments, the sintering temperature may be at least about800° C., e.g., when silver is used. The sintering temperature may begenerally in a range of about 750° C. to about 950° C., and moreparticularly, between about 850° C. to about 945° C. The plurality ofmetal-coated dielectric particles may be sintered for a duration in arange of about 10 minutes to about 1000 minutes, though othertemperatures and sintering durations can also be utilized.

In some embodiments of the above method, some of the metal incorporatedin the dielectric layer migrates to at least one of the electrodesduring the high temperature sintering process so as to form a thindielectric layer adjacent that electrode, where the thin dielectriclayer is substantially free of the metal (“depletion layer”). In otherwords, the depletion layer, which can have a thickness in a range ofabout 0.01 micron to about 20.0 microns, e.g., in a range of about 0.01micron to about 10.0 microns, may be formed in-situ during the sinteringprocess. In some embodiments, the metallic constituent(s) of at leastone of the electrodes and that of the metal incorporated in thedielectric are selected to have at least one component in common tofacilitate in-situ formation of the depletion layer, e.g., byfacilitating “wicking” of a portion of the metal incorporated in thedielectric to the electrode.

The inventive system demonstrates that a metalized dielectric layer maybe formed in-situ during sintering. A capacitor structure may be createdin-situ during the sintering process of a multi-layer ceramic capacitor(MLCC). For example, in a precious metal MLCC, silver in a silverdielectric composite forming a dielectric layer tends to migrate intothe electrode layer during sintering of the multilayer ceramiccapacitor. The dielectric left in the silver dielectric composite formsthe dielectric layer in the capacitor structure. The thickness of thisthin dielectric layer can vary depending upon the parameters, such as,type of the metal, or alloy, percentage of the metal content, sinteringtemperature and duration, dielectric compositions. Typically, athickness from about 0.1 to about 20 microns can be achieved, and moretypically, between about 0.2 to about 5 microns. The capacitor structurecreated in-situ during sintering may complement with the current tapebuildup technology to manufacture an improved MLCC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B collectively illustrate a modified manufacturing processaccording to an embodiment for generating a three-dimensionalmulti-layer ceramic capacitor having EDE tri-layers.

FIG. 1C illustrates a cross-sectional metallurgical microstructure viewof a MLCC produced when a metal coated dielectric tape is used in themethod of FIG. 1.

FIG. 2A illustrates a configuration of a MLCC prior to sintering.

FIG. 2B illustrates a configuration of a MLCC with insulation at itsends comprised of a dielectric.

FIG. 2C illustrates a comparative example of a MLCC in which theAg-dielectric composite is electrically shorted.

FIG. 3 illustrates a MLCC with an asymmetric layout in which both theelectrode and Ag-dielectrics are printed on a surface of a dielectrictape.

FIG. 4 illustrates a symmetric layout and pre-sintering stage of a MLCCrelative to the asymmetric layout of the exemplary embodiment of FIG. 3.

FIG. 5A illustrates an exemplary MLCC before sintering in whichdielectric layers have not been formed yet.

FIG. 5B illustrates a cross-sectional metallurgical microstructure viewof an exemplary MLCC after sintering.

FIGS. 6A-6C illustrate cross-sectional metallurgical microstructureviews produced by a scanning electron microscope (SEM) of a first sampleMLCC using Ag coated dielectric tapes after sintering the MLCC atapproximately 940 C for approximately five hours.

FIGS. 7A-7D illustrate cross-sectional metallurgical microstructureviews produced by an optical microscope of other first sample MLCCscorresponding to the sample MLCC of FIGS. 6A-6C.

FIGS. 8A-8C illustrate cross-sectional metallurgical microstructureviews produced by a scanning electron microscope (SEM) of a secondsample MLCC using Ag coated dielectric tapes after sintering the MLCC atapproximately 940 C for approximately five hours.

FIGS. 9A-9D illustrate cross-sectional metallurgical microstructureviews produced by an optical microscope of other second sample MLCCcorresponding to the sample MLCC of FIGS. 8A-8C.

FIGS. 10A-10C illustrate cross-sectional metallurgical microstructureviews produced by a scanning electron microscope (SEM) of a third sampleMLCC using Ag coated dielectric tapes after sintering the MLCC atapproximately 975 C for approximately one hour.

FIGS. 11A-11D illustrate cross-sectional metallurgical microstructureviews produced by an optical microscope of other third sample MLCCscorresponding to the sample MLCC of FIGS. 10A-10C.

FIGS. 12A-12C illustrate cross-sectional metallurgical microstructureviews produced by a scanning electron microscope (SEM) of a fourthsample MLCC using Ag coated dielectric tapes after sintering the MLCC atapproximately 975 C for approximately one hour.

FIGS. 13A-13D illustrate cross-sectional metallurgical microstructureviews produced by an optical microscope of other fourth sample MLCCscorresponding to the sample MLCC of FIGS. 12A-12C.

FIG. 14 illustrates a cross-sectional view of a single EDE tri-layerthat forms one exemplary embodiment of a three-dimensional capacitor,wherein three-dimensional structures are formed from conductive coatingson dielectric particulates.

FIG. 15 illustrates a cross-sectional view of a single EDE layer thatmay form another exemplary embodiment of a three-dimensional capacitor,wherein three-dimensional structures are formed from metal particlesmixed into the dielectric slurry of coated dielectric particles.

FIG. 16 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein metal particles are impregnated into the dielectricgreen tape.

FIG. 17 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein metal particles are impregnated into the dielectricgreen tape and the conductor plates comprise a layer of low meltingpoint electrode material adjacent to the dielectric layer.

FIG. 18 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein metal coated particulate are used to create theconductive layers between which a dielectric layer is sandwiched.

FIG. 19 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein a metal coated ceramic layer is formed between thedielectric layer and the electrode layers.

FIG. 20 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein three-dimensional structures protrude perpendicularlyfrom the primary conductor layers into the dielectric layer.

FIG. 21 illustrates a cross-sectional view of a single EDE tri-layerthat may form another exemplary embodiment of a three-dimensionalcapacitor, wherein three-dimensional structures protrude from theprimary conductor layers into the dielectric layer.

FIG. 22 illustrates a cross-sectional view of another exemplaryembodiment of a three-dimensional capacitor having a plurality ofdiscrete metal inclusions in the dielectric layer but without a“depletion layer” adjacent to the electrodes.

DETAILED DESCRIPTION

The presently disclosed embodiments, as well as features and aspectsthereof, are directed towards providing a capacitor, and methods ofmanufacture, for improving capacitance efficiency. More specifically, animproved capacitor may be constructed with electrode layers havingthree-dimensional aspects at the point of interface with a dielectric.Advantageously, embodiments of a three-dimensional capacitor drasticallyreduce the space footprint that is required in a circuit to accommodatethe capacitor, when compared to current capacitor designs known to oneof ordinary skill in the art. Increased capacitive density can berealized without necessarily requiring high k (high constant) dielectricmaterials, additional “electrode-dielectric-electrode” arrangements inan ever increasing stack, or serially stringing together multiplecapacitors.

In some embodiments, a capacitor, such as an MLCC, is disclosed thatincludes one or more metalized dielectric layers, each of which isdisposed between two electrodes adapted for coupling to voltageterminals. It has been discovered that a significant amount of metal canbe incorporated within a dielectric layer while ensuring that theincorporated metal forms separate metallic inclusions that do not form apercolation network. In fact, in some cases, the volume fraction of theincorporated metal can exceed the percolation threshold without leadingto the occurrence of percolation. For example, in some embodiments, thevolume fraction of the metal in the dielectric layer can be at leastabout 40%. Further, in some embodiments, a depletion dielectric layer(i.e., a dielectric layer that is substantially, and preferablyentirely, free of the metal) separates the metalized dielectric layerfrom at least one, and preferably, both electrodes between which themetalized layer is disposed. In this manner, capacitors exhibiting ahigh capacitance, and as well as high capacitive densities, can beachieved.

Exemplary embodiments of MLCCs are disclosed herein in the context ofceramic based capacitors, however, one of ordinary skill in the art willunderstand that various embodiments of a MLCC may not necessarilycomprise ceramic based components and, as such, the scope of the presentdisclosure will not be limited to ceramic based embodiments. Moreover,the dielectric, anode and cathode layers of the disclosed embodimentsmay at times be generally referred to herein as “plates” or “layers.”However, the present disclosure shall not be interpreted such that theconductive or dielectric layers must be “rigid” or “stiff” plates in allembodiments of a three-dimensional capacitor. Rather, the term “plate,”as taken in context with a particular exemplary embodiment beingconveyed, will be understood to include any component layer, or methodof creation thereof, including rigid plates or plates created from theapplication of inks, paste, mechanics of deformable bodies, etc. Thatis, it will be understood that the term “plate” simply refers to aparticular layer within a three-dimensional capacitor, such layerlimited only by the features and aspects that may be described relativeto the disclosure of the exemplary embodiments with which it isassociated.

Generally, the particular embodiments described in the presentdisclosure are offered for illustrative purposes only and will not beconstrued to limit the scope of MLCC. Moreover, while variousembodiments of a MLCC may utilize different component or materialchoices, the exemplary materials described relative to the illustrativeembodiments in the present disclosure are not intended as acomprehensive listing of materials or components that may be includedwithin a MLCC. Materials used to create the MLCCs and, in particular,the features of capacitor such as the anode layer, cathode layer,terminals, conductive protrusions, dielectric or “green tape” layer, mayvary from one embodiment to another (e.g., based on particularapplications for which the capacitor is intended) and, although perhapsserving to generate a novel feature or aspect of a certain embodiment,will not limit the scope of the disclosure.

Material choices for the various components or features of a giventhree-dimensional capacitor include, but are not limited to: for theelectrodes—silver (e.g., about 100% percent by weight), silver palladiumalloy (such as about 95% Ag to about 5% palladium percent by weight),palladium, and other precious metals such as, but not limited to, gold,platinum, iridium, and their alloys, as well as refractory metals suchas, but not limited to, tungsten, molybdenum, tantalum, niobium,hafnium, and rhenium, and base metals such as, but not limited to,nickel, nickel alloy, copper and copper alloys; for the dielectriclayer: ceramic and glass-ceramic, precious metal coated ceramics suchas, but not limited to, silver-coated ceramics, palladium-coatedceramics, silver palladium coated ceramics, etc. as well as silvercoated formulated barium titanate based dielectrics, silver coated glassbeads, and inorganic oxides such as, but not limited to, alumina andtantalum oxide.

Turning now to the figures, where like reference numerals represent likeelements throughout the drawings, various aspects, features andembodiments of exemplary three-dimensional capacitors and methods ofmanufacture will be presented in more detail. The examples as set forthin the drawings and detailed description are provided by way ofexplanation and are not meant as limitations on the scope of a MLCC, andin particular, a three-dimensional capacitor.

Methods for making a three-dimensional capacitor or the specificmaterials of construction that may be included within athree-dimensional capacitor are described. A MLCC, such as athree-dimensional capacitor, thus includes any modifications andvariations of the following examples that are within the scope of theappended claims and their equivalents as understood to one of ordinaryskill in the art.

According to exemplary embodiments of MLCC, by using metal coatedceramic particles or a silver dielectric composite in place of uncoatedceramic particles in the dielectric layer, a modified manufacturingprocess is described that may be used to create MLCCs, such as athree-dimensional capacitor embodiment. Coated dielectric materials or ametal-dielectric composites or mixtures may be merged with an improvedmanufacturing method to render a MLCC.

Some embodiments of a three-dimensional capacitor include multi-layerceramic capacitors (MLCC) or the like and, therefore, it will beunderstood that many of the embodiments of three-dimensional capacitorthat are described and depicted in the present disclosure are intendedto only represent a single “electrode-dielectric-electrode” arrangement(EDE) that may represent a single tri-layer within a MLCC.

FIGS. 1-2 collectively illustrate one exemplary manufacturing method 101that may be used to generate a MLCC having EDE tri-layers according toan exemplary embodiment of the invention. Referring to FIG. 1, in themanufacturing process for a MLCC, a ceramic powder 205 is mixed (step105) into a carrier such as, but not limited to, a compound which maycontain a solvent, polymer resin and additives such as a dispersingagent, to form a ceramic slurry 210.

The ceramic slurry 210 is used to cast the “green ceramic tape” 215 inthe tape casting step 110 of the process. The green tape 215, havingbeen made from the ceramic powder slurry, will eventually function as adielectric layer of a capacitor. Although the exemplary green tape isdescribed above as being formed from a ceramic slurry, it will beunderstood that embodiments of the invention may include green tapecomponents made from materials other than, or in addition to, ceramicssuch as, but not limited to, formulated barium titanate baseddielectrics, glass ceramics such as, but not limited to, Ca—B—Si—Osystem glass ceramics used in low-temperature co-fired ceramics, andalumina glass ceramics used in high-temperature co-fired ceramics andvarious metal coated ceramics and inorganic oxides and compounds. Themetal used for coating or mixing can include, but is not limited to,silver-palladium alloys (such as the percent by weight composition ofsilver palladium in the range of about 95% Ag and about 5% Pd, morepreferably about 90% Ag and about 10% Pd, and most preferably about 70%Ag and about 30% Pd) as well as palladium, palladium alloys, platinum,platinum alloys, silver, silver alloys, gold, gold alloys and otherprecious metals and their respective alloys, such as, iridium, Rhodium,ruthenium, as well as base metals, such as, but not limited to, copper,nickel, iron, cobalt, manganese, titanium, zinc, and refractory metalssuch as, but not limited to, tungsten, molybdenum, zirconium, tantalum,and niobium.

Surface texturing of the green tape may also be made using a mechanicalroller. For example, after rolling on top of the green tape, the textureon the roller may be transferred onto the green tape. Later, once cast,the green tape 215 advances in the exemplary process to be screenprinted at step 120.

Prior to screen printing at step 120, an electrode metal powder 220 ismixed (step 115) with a carrier compound to form electrode ink 225. Theelectrode ink 225 is screen printed in step 120 onto the ceramic greentape 215 to form a single dielectric-conductive bi-layer of an eventualMLCC.

Step 120 is one main aspect of this inventive system and method asdescribed below in connection with FIGS. 1C-13. A silver dielectriccomposite or mixture may be used in this screen printing step 120, alsoreferred known to one of ordinary skill in the art as the “green tapestage.” The silver dielectric composite may include a metal (e.g.,silver) coated dielectric tape, a dielectric mixed with metal (e.g.,silver) powder, metal (e.g., silver) coated ceramic particles, or anyother ways to form a metal dielectric composite as understood by one ofordinary skill in the art. In some embodiments in which metal-coatedceramic particles are employed, the ceramic particles have a size in arange of about 0.01 micron to about 10.0 microns.

If a dielectric composite comprising dielectric particles mixed with ametal (i.e. silver) powder or metal (i.e. silver) coated dielectrictapes are used in place of the exemplary non-coated ceramic powder 205described above in step 120, then the MLCCs illustrated in FIGS. 14-22,or FIG. 1C-13 may be formed. For example, in some embodiments,silver-coated ceramic particles may be employed. As discussed in moredetail below, when certain processing parameters are employed, e.g., asintering temperature in a range of about 850° C. to about 950° C. forsilver coated ceramic particles, a portion of the metal migrates from aregion in proximity to at least one of the electrodes to that electrode,thereby generating a depletion layer (i.e., a layer that issubstantially free of the metal) in the proximity of that electrode. Insome cases, the metal that has migrated to the electrode causes anincrease in the surface layer of that electrode, e.g., in the form offinger-like protrusions, which can in turn enhance the capacitance of acapacitor to be formed through subsequent processing steps. In someembodiments, the electrode has at least one metal constituent in commonwith the metal incorporated into the dielectric to facilitate themigration of the metal in a thin composite metal-dielectric layer inproximity of the electrode to that electrode so as to generate adepletion layer.

As steps 105 through 120 are repeated, the multiple screen printed greentape sheets 230, each sheet comprising a single dielectric-conductivebi-layer, are stacked at step 125 such that EDE tri-layers are createdvia the repeated juxtaposition of a screen printed conductive layer withthe bottom surface of the green tape of a subsequent sheet. The stackresulting from step 125 is laminated together at step 130 in alamination process. The resulting laminated stack 235 is then convertedat step 135 into individual ceramic green chips 240 include multipleinterleaved EDE tri-layers.

In FIG. 1B, the method or method 101 continues with the individualceramic green chips 240 being exposed to a firing process at step 140.In the firing process (step 140), the green ceramic chips 240 may besent through a belt furnace or the like to cause the organics in theaforementioned slurries to be removed, thereby sintering the greenceramic chip 240 into a ceramic capacitor chip 245 comprising EDEtri-layers. The sintering temperature can be selected, e.g., based onthe metal used to form the dielectric-conductive layer. Generally, thesintering temperature is sufficiently high to causes at least partiallymelting of the metal. By way of example, the sintering temperature canbe in a range of about 750° C. to about 980° C. for silver coatedceramics, while about 1100° C. to about 1500° C. for nickel coatedceramic in base metal MLCC.

At step 150, the sintered ceramic capacitor chip 245 may then bemetalized at each of two ends via dipping into a termination ink 250that was mixed (step 145) from a conductive metal powder 255. Thetermination metallization provides internal connection betweenalternating conductive plates (anode to anode and cathode to cathode) aswell as electrical contact points for circuit board applications. Theterminated chips 260 are then dried and fired again at step 155 in atermination firing process to become a MLCC 265. In some embodiments,the firing temperature can be, e.g., in a range of about 750° C. toabout 900° C. Finally, at step 160, tin plating may be applied to theMLCCs 265 in a plating process to protect the termination metallizationand provide for ease of soldering connections. As is known to one ofordinary skill in the art of manufacturing, the MLCCs 265 may then gothrough a testing process at step 165 for quality control prior toemployment in a circuit (step 170).

Modified Manufacturing Process Coupled with Unique Component Selectionfor Constructing the 3-D Capacitors of FIGS. 1C-13: Metal CoatedDielectric Tapes or Slurries with Printed Coatings

Post-Sintering View of an Actual Sample Using Metal Coated DielectricTapes: FIG. 1C

Referring now to FIG. 1C, this figure illustrates a cross-sectional viewof a MLCC 100A produced when a silver coated dielectric tape 30 is usedin the method of FIG. 1A-1B. This figure was produced using a scanningelectron microscope at a magnification level of approximately 1000times. The MLCC 100A comprises several layers: an metal electrode layer10, a dielectric layer 20A (herein also referred to as depletion layer20A), a metal-dielectric tape layer 30 (herein also referred to asmetalized dielectric layer 30), and a dielectric layer 40. Thedielectric layer 40, in some embodiments, may have a thickness that isgreater than the thickness of the depletion layer 20A, e.g., in thisexample by about six times. Also visible are pockets or inclusions ofmetal 605 that migrates during sintering. It is noted here that thedielectric layer 20A is formed in-situ from the silver migration out ofthe silver-dielectric layer 30.

The following are exemplary materials used to form this MLCC structure100. The electrode layer 10 comprises a 95/5 Ag/Pd (approx. 95% silverwith approx. 5% palladium). The dielectric layer 40 may comprise a lowtemperature finable COG type titanate dielectric, sold as a commerciallyavailable product under the product name of VLF-220Aq3 manufactured byMRA Laboratories, and the metal-dielectric (i.e. Ag-dielectric)composite tape layer 30 may comprise an approximately 30% (by weight)silver coating of VLF-220Aq3. The sintering temperature may range fromabout 940° C. to about 975° C. The size of the capacitor chips mayinclude sizes like 2018 (approx. 0.20 inches by approx. 0.18 inches).Typically, six active layers are used to make the capacitor chips.Typical dielectric layer thickness is about 0.001 inch (about 25microns). Other sizes may be included which are within the scope of theinvention.

Referring now to FIG. 1C which is a cross-sectional view produced by anelectron microscope after sintering, the capacitor 100A may beconstructed by printing an Ag/Pd electrode 10 on top of Ag-dielectriccomposite tape 30 and the Ag-dielectric composite tape 30 is insulatedby the dielectric layer 40. The dielectric layer 40 may have a thicknessof about thirty microns; while the Ag-dielectric composite tape 30 has athickness of about ten microns after sintering.

In the scanning electron microscopic image, FIG. 1C, the lighter shadedmaterials are metal, Ag/Pd in electrode 10, and Ag in Ag-dielectriccomposite layer 30. The dark background shaded areas comprise thedielectric. A dielectric layer 20A, formed during the sintering processby the migration of silver in Ag-dielectric composite to the electrode10, having a thickness of about five microns, may be seen clearlybetween the Ag/Pd electrode 10 and the remaining Ag-dielectric compositelayer 30. Within the Ag-dielectric composite tape 30, inclusions orpockets of metal 605 are observed. An approximate increase of about fivetimes (500%) is observed when comparing the capacitance of capacitor100A to the capacitance of a control capacitor having the samedimensions and materials made only with pure dielectric tapes andwithout incorporation of metal in the dielectric.

Pre-Sintering Views: Exemplary Layer Designs Using MetalcoatedDielectric Tapes—FIGS. 2A-5A

Referring now to FIG. 2A, this figure shows another exemplary capacitorstructure 100B that may be formed using only the Ag-dielectric compositetape 30 without any dielectric layer 40. Specifically, FIG. 2Aillustrates a configuration of a MLCC 100B prior to sintering. FIG. 2Ashows the configuration of the capacitor 100B at the green stage beforesintering (Steps 130-135, FIG. 1A). In FIG. 2A, the Ag/Pd electrode 10is printed onto the Ag-dielectric composite tape 30 directly. TheAg-dielectric composite tape 30 is insulated electrically at one of itsends relative to a termination 50A. The terminations 50A, 50B may bemade from materials that include, but are not limited to, silver.

Insulation at one of the ends of the Ag-dielectric composite tape 30 maycomprise a dielectric 40 or an air-filled cavity (not illustrated)formed by fugitive inks Insulation may also be formed using the Ag/Pdelectrode 10B during sintering as illustrated in FIG. 2B. In otherwords, FIG. 2B illustrates a configuration of a MLCC 100C withinsulation at its ends comprising an Ag-dielectric composite tape 30.

The dielectric layers 20A described in connection with FIG. 1C have notformed yet at this stage in FIG. 2B as illustrated in this intermediatestage or phase of the method. Upon sintering, the silver in theAg-dielectric composite tape 30 migrates and forms a dielectric layer20A (shown in FIG. 1C) in-situ within the dielectric composite tape 30.The electrode layer 10 and the Ag-dielectric composite tape 30, togetherwith the dielectric layer 20A formed during sintering as shown in FIG.1A, may form the capacitor structure 100C of FIG. 2B. Note that twodielectric layers 20A (not shown in this FIG. 2B) may be formed in eachAg-dielectric composite tape 30.

FIG. 2C illustrates a comparative example of a MLCC 100D in which theAg-dielectric composite 30 is electrically shorted. Specifically, FIG.2C shows a comparative example of a capacitor structure 100D, in whichall the Ag-dielectric composite layer 30 is electrically short relativeto the embodiments of FIGS. 2A and 2B, when no dielectric insulation 40or cavity is used at one end of the Ag-dielectric composite tape 30 neartermination 50A. However, shorting of electrical currents that typicallypass through the Ag-dielectric layer 30 may be prevented if silvermigration is permitted or promoted to occur effectively during thetermination process when terminations 50 are added. This exemplaryembodiment of FIG. 2C also illustrates a pre-sintering stage which meansthat the dielectric layers 20A (as illustrated in FIG. 1) have not beenformed yet.

Paste can be used to form the Ag-dielectric composite layer 30, insteadof Ag-dielectric composite tape 30. The Ag-dielectric composite layer 30usually has to be thick enough to make sure that silver-dielectric layerhas sufficient metal material to form an electrode within the layer 30after silver migration occurs during the sintering stage for thecapacitor structure 100. Typical thickness of the Ag-dielectriccomposite layer 30 for this embodiment of FIG. 2C generally includesmagnitudes of about ten microns as stated in the description of FIG. 1C.

It is understood by one of the ordinary skill in the art that thein-situ formed dielectric layer thickness is not only affected by theprinted layer thickness, but also influenced by other factors, such as,sintering temperature, and the chemistry of the dielectric and thenature of the metal used to form the metal-dielectric composite. It isalso understood that the thickness given here should not be used as alimiting factor, and that the thinner the in-situ formed dielectriclayer generally results in higher or increased capacitance performance.

FIG. 3 illustrates a MLCC 100E with an asymmetric layout in which boththe electrode 10 and Ag-dielectrics 30 are printed on a surface of adielectric tape 70. Specifically, FIG. 3 illustrates another exemplaryembodiment of a capacitor structure 100E, in which both the electrode 10and the three Ag-dielectric layers 30A, 30B, and 30C are printed on topof a dielectric tape 70. In this configuration, two types ofsub-capacitor structures may be formed which have different dielectriclayer thicknesses.

FIG. 3 shows the capacitor configuration at the green stage beforesintering, therefore, the dielectric layer 20A formed during sintering,as shown as in FIG. 1, has not formed yet. One sub-capacitor structureis formed after sintering between the Ag/Pd electrode 10 and an adjacentprinted first Ag-dielectric composite 30A. Here the remainingAg-dielectric 30A is one electrode and the Ag/Pd 10 is the otherelectrode, together with the dielectric layer 20A (not shown) formedin-situ as the dielectric depletion layer to form the thin capacitorstructure. The other capacitor structure is formed after sinteringbetween the Ag/Pd electrode 10 and a second printed Ag-dielectriccomposite 30B across to the dielectric tape layer 70. It is clear thatthe first capacitor sub-structure has much higher capacitance due to thethinner layer of dielectric formed in-situ, than the second type whichis a conventional structure.

The printed first, second, and third Ag-dielectric composites 30A, 30B,30C are different from the Ag-dielectric composite tape 30 of theembodiment of FIG. 2C in the way these materials are formed during theirrespective component manufacturing. The Ag-dielectric composite tape 30of FIGS. 2A, 2B, and 2C is formed by tape casting from a slurry, whilethe printed first Ag-dielectric composites 30A, 30B, and 30C are formedby printing from a paste. The functional material, Ag-dielectriccomposite powder, may be the same. Once each capacitor 100D (FIG. 2C)and 100E (FIG. 3) is formed, the composite tape 30 and composites 30A,30B, and 30C function similarly with respect to the operation of theoverall capacitor 100D, 100E.

FIG. 4 illustrates a symmetric layout and pre-sintering stage of a MLCCrelative to the asymmetric layout 100E of the exemplary embodiment ofFIG. 3. Specifically, in this exemplary embodiment of FIG. 4, theAg-dielectric composites 30A, 30B, 30C (formed from a paste) arepositioned in an alternating fashion relative to the terminations 50A,50B. Since FIG. 4 schematically illustrates a pre-sintering stage,dielectric layers 20A (illustrated in FIG. 1) have not been formed.

Meanwhile, in the exemplary embodiment of FIG. 3, the Ag-dielectriccomposite layer 30 is only in contact with one of the terminations 50B.

FIG. 5A illustrates an exemplary MLCC 100G before sintering in whichdielectric layers 20A have not been formed yet. Specifically, FIG. 5Adepicts another exemplary capacitor structure 100G at the green stagebefore sintering which means that dielectric layers 20A (illustrated inFIG. 1C) have not been formed yet. In this exemplary embodiment, boththe Ag-dielectric composites 30A, 30B, 30C (formed from a paste) and theAg/Pd electrode 10 are printed on top of the dielectric tape 70. TheAg-dielectric composites 30A, 30B, 30C are printed larger relative tothe area of the Ag/Pd electrode 10 in order to prevent shorting ofelectrical currents. In this exemplary embodiment of FIG. 5A, surfacearea of the composites 30A, 30B, 30C relative to the surface area of theelectrode 10 are about 20% larger. The capacitor structure 100G also hasdielectric tape layers 70 which are made of the same material as theones illustrated in FIG. 3.

Post Sintering View: Layer Designs of an Actual Sample Using MetalcoatedDielectric Tapes—FIG. 5B

FIG. 5B illustrates a cross-sectional view of an exemplary MLCC 100Hafter sintering. Specifically, FIG. 5b shows the capacitor structure100H after sintering. FIG. 5b is a cross-sectional view produced by anoptical microscope and illustrates an exemplary embodiment of acapacitor structure 100H in which the silver in the printedAg-dielectric composite 30 (formed from paste as illustrated inpre-sintering stages of FIGS. 2A-5A) that is printed on dielectric tapes70 is permitted to completely migrate into the electrode 10 in order toform the dielectric layers 20A in-situ during sintering. In FIG. 5B, thelighter shaded material is the Ag/Pd electrode material 10, while thedark background shaded material are the dielectric layers 70 and 20A.

As shown in FIG. 5B, silver in the Ag-composite layer 30 (as illustratedin pre-sintering FIGS. 2A-5A) completely migrates or moves to theelectrode layer 10 to form layer 20A and the resultant capacitorstructure. “In situ” as used in this description means “duringsintering.” An increase of about six times (about 600%) of capacitanceis observed when comparing this capacitor structure 100G and 100H to aconventional capacitor having the same size and formed of the samematerials for the electrodes and the dielectric layer that does not havethe printed thin capacitor formed from silver migration duringsintering. It is also noted that the dielectric breakdown voltageusually does not degrade due to the thin dielectric layer.

In the above described exemplary embodiments, the increase in thecapacitance is usually due to the formation of thin dielectric layer 20Aafter silver migration from the Ag-dielectric composite 30. However, themigration of silver to the electrode 10 also creates opportunities toform an uneven surface at the electrode/dielectric interface. The roughsurface usually increases the surface area of the electrode 10 and maycontribute to the increase in capacitance.

These changes which cause the uneven surface at the electrode/dielectricinterface may be affected by the sintering temperature. In the exemplaryembodiments of the capacitors illustrated in FIGS. 1C-5, an increase ofabout ten percent in capacitance has been observed when the capacitors100 are fired at lower temperature.

It should be pointed out that a capacitor 100 (G&H) may also be simplymade by replacing the Ag-dielectric composite 30—with a pure dielectric.This is equivalent to when the silver percentage approaches zero in theAg-dielectric composite 30. In the above exemplary embodiments, silveris used as the metal in the Ag-dielectric composite 30. Other metals oralloys can be used for Ag-dielectric composite 30, such as, but notlimited to, Ni and Ni/Cu in base metal MLCC, and Ag/Pd alloys used inprecious metal multilayer ceramic capacitors (MLCCs). In some cases, themetal content in the Ag-dielectric composite 30 has to be high enough toform a conductive layer after migration. Factors which affect or impactthe thickness of the in situ formed dielectric layer 20A, for example,dielectric layer 20A illustrated in FIG. 1C, dielectric layer 30 in FIG.5B, are the melting point of the metal or alloy in the metal dielectriccomposite 30, sintering temperature, and the amount of metal content inthe metal dielectric composite 30. The glass in the dielectric 40, ordielectric 70 may also have a significant impact on the thickness of thein situ formed dielectric layers 20A.

Post Sintering Views of Test Samples: Layer Designs Using MetalcoatedDielectric Tapes FIGS. 6-13

FIGS. 6-13 illustrated black and white photos of scanning electronmicroscope (SEM) and light microscopy views of four samples of MLCClayer designs using metal (i.e. —Ag) coated dielectric tapes. These Agcoated dielectric tapes are used to make up approximately ⅓ of the totaldielectric thickness forming the layers of the MLCC. The other twothirds of each MLCC comprise normal dielectric tapes. In these samples,it was noted one layer that appears thinner was not contacted by a sheetof the Ag coated dielectric tape. This was done purposely to guardagainst the entire structure becoming conductive, as with other testsamples that did not work/perform because the entire structure becameconductive.

The cover layers of these sample MLCCs are also made from normaldielectric tapes. One hundred MLCC's designated (A) were processed sothat the orientation remained the same, whereby the internal electrodewas printed directly upon the Ag coated dielectric tape. These partswere burned out and sintered so that the Ag coated layers would facedownward (toward the Al2O3 setter). Forty-eight MLCC's were processed sothat each of the coated layers would face upward (away from the setter)during burnout and firing (label B). Each group (A and B) of the foursamples illustrated in FIGS. 6-13 was sub-divided and fired using twoprofiles, 940 C/5 hr. sintering and 975 C/1 hr. sintering

Observations of Samples Illustrated in FIGS. 6-13

There was a marked improvement in sintered microstructure for thisdesign compared to prior samples referred to FIG. 2C. The 975*C/1 hr.sintering appears to be considerably denser than the 940*C/5 hr.profile.

In each sample illustrated in FIGS. 6-13, regardless of orientationduring binder burnout and firing, the Ag in the coated tape portion ofthe dielectric layer 30 seems to actually migrate away from the 95Ag/5Pdinternal electrode 10 which is an unexpected result to one of ordinaryskill in the art, and appears to have minimal effect on electricalperformance. This was unexpected because in some layers the Ag movedupward against the force of gravity. Meanwhile, one of ordinary skill inthe art would expect the Ag to move downward because of the force ofgravity.

Another observation of these samples illustrated in FIGS. 6-13 is thatthe Ag migration appears to stay largely within the coated tapedielectric layer 30 and congregates as what appears to be rather puredielectric layer 20A. Silver in the silver-dielectric composite migratesinto the electrode layer, and also migrates to form pockets 605 of Agmetal. These pockets 605 appear much more frequent in the faster profilesintering trial (LT-3088A, sint. 975 C/1 h—FIGS. 10-11 and LT-3088B,sint. 940 C/1 h FIGS. 12-13), but larger in size in the slower trial(LT-3088A, sint. 975 C/5 h—FIGS. 6-7 and LT-3088B, sint. 940 C/5 h FIGS.8-9). Again, this suggests that much of the Ag is accumulating aspockets 605 of pure Ag. Another observation of these samples were thatnone of the samples cross-sectioned exhibited delaminations.

Electrical results (approximately 1 kHz, 1 Vrms) 940° C./5 hrs. 975°C./1 hr. LT-3088A non-shorts 7/50 50/50 LT-3088B non-shorts 4/24 19/24LT-3088A cap range (pico F) 20.37-52.89 12.06-26.36 LT-3088B cap range(pico F) 36.26-70.10 18.60-24.24 (A) effective dielectric constant 84.7642.67 (B) effective dielectric constant 113.5  39.24

The effective dielectric constant was calculated for the single partfrom each group that exhibited the largest capacitance. As understood byone of ordinary skill in the art, the effective dielectric constant iscalculated based on the observed capacitance and the dimensions of thecapacitor. Dielectric loss was measured at about 0.00% for each group,with the exception of LT-3088A sintered at 940*C/5 hrs. which rangedfrom about 0.00 to about 0.03%. Again, these ranges suggest minimalreaction between Ag and the normal dielectric portion of the effectivelayers.

Meanwhile, the normal dielectric constant (K) in MLCC form for thisdielectric is typically about 23. K-squares were also made with this run(having no internal 95Ag/5Pd electrode layers, but containing the samelayers of Ag coated dielectric as the MLCC's) and the measured K wasfound to be approximately 24.5. Again, this suggests that the Ag islargely non-reactive with the dielectric, and does not contribute much,if anything, to conduction in this form as understood by one of ordinaryskill in the art.

Summary of Observations for Samples Illustrated in FIGS. 6-13 andDescribed in Further Detail Below:

A MLCC 3-D capacitor formed from metal-coated (i.e. Ag-coated)dielectric tapes appears to increase the effective dielectric constant Kand capacitance of the entire MLCC significantly. In the single case ofLT-3088B, as noted above, the increase appears to be approximately fivetimes relative to a MLCC formed without any metal-coated dielectrictapes.

Detailed Description of Four Samples Illustrated in FIGS. 6-13

FIGS. 6-13 illustrate the four samples discussed above. Each sample usesthe following reference numerals for its various layers: Ag electrodelayer (10); dielectric layer (20A) formed between Ag electrode layer(10) and the Ag coated dielectric tape (30); pockets of Ag metal (605);and un-coated, standard/regular dielectric tape (70).

Specifically, FIGS. 6A-6C illustrate cross-sectional views produced by ascanning electron microscope (SEM) of a first sample MLCC 100-1(LT-3088A) using Ag coated dielectric tapes 30 after sintering the MLCC100-1 at approximately 940° C. for approximately five hours of soaking.

More specifically, FIG. 6A illustrates a SEM cross-sectional view of thefirst sample MLCC 100-1 at a magnification level of approximately 500times. Several instances of the layers, including Ag electrode layers10, dielectric layers 20A, and Ag coated dielectric tape layer 30 arepresent. Pockets of Ag metal 605 are also visible.

FIG. 6B illustrates a SEM cross-sectional view of the first sample MLCC100-1 of FIG. 6A at a magnification level of approximately 2000 times.Several instances of the layers (but fewer than those illustrated inFIG. 6A) are visible, including Ag electrode layers 10, dielectriclayers 20A, and Ag coated dielectric tape layer 30 are present. Pocketsof Ag metal 605 are also visible.

FIG. 6C illustrates a SEM cross-sectional view of the first sample MLCC100-1 of FIG. 6A at a magnification level of approximately 5000 times.Only the Ag coated dielectric tape layer 30 is visible. Pockets of Agmetal 605 formed within the dielectric tape layer 30 are also visible.As noted above, the pockets 605 of metal (i.e. —Ag) in this exemplaryfirst sample MLCC 100-1 (and the second exemplary sample MLCC 100-2)having longer soak times are larger in size relative to the pockets 605of the third and fourth sample MLCCs 100-3, 100-4 having longer soaktimes but are less frequent in number.

FIGS. 7A-7D illustrate cross-sectional views produced by an opticalmicroscope of other sample first sample MLCCs 100-1 (LT-3088A)corresponding to the one illustrated in FIGS. 6A-6C. Specifically, FIGS.7A-7C illustrate an optical microscope cross-sectional view of a firstsample MLCC 100-1 at a magnification level of approximately 100 times.In FIGS. 7A-7C, several layers, including the Ag electrode layer 10; Agcoated dielectric tape (30); and un-coated, standard/regular dielectrictape (70) are visible. (The pockets or inclusions of metal 605 are notvisible.) FIG. 7A illustrates a first embodiment of the first sampleMLCC 100-1 while FIG. 7B illustrates a second embodiment of a firstsample MLCC 100-1 and FIG. 7C illustrates a third embodiment of a firstsample MLCC 100-1, where each embodiment was manufactured in the samebatch or set of MLCCs 100.

FIG. 7D illustrates an optical microscope cross-sectional view of afirst sample MLCC 100-1 at a magnification level of approximately 1000times. In this FIG. 7D, several layers including Ag electrode layers 10,dielectric layers 20A, and Ag coated dielectric tape layer 30 arepresent. Pockets of Ag metal 605 are also visible.

FIGS. 8A-8C illustrate cross-sectional views produced by a scanningelectron microscope (SEM) of a second sample MLCC 100-2 (LT-3088B) usingAg coated dielectric tapes after sintering the MLCC at approximately 940C for approximately five hours of soaking More specifically, FIG. 8Aillustrates a SEM cross-sectional view of a second sample MLCC 100-2 ata magnification level of approximately 500 times. Several instances ofthe layers, including Ag electrode layers 10, dielectric layers 20A, andAg coated dielectric tape layer 30 are present. Pockets of Ag metal 605are also visible.

FIG. 8B illustrates a SEM cross-sectional view of the second sample MLCC100-2 of FIG. 8A at a magnification level of approximately 2000 times.Several instances of the layers (but fewer than those illustrated inFIG. 8A) are visible, including Ag electrode layers 10, dielectriclayers 20A, and Ag coated dielectric tape layer 30 are present. Pocketsof Ag metal 605 are also visible.

FIG. 8C illustrates a SEM cross-sectional view of the second sample MLCC100-2 of FIG. 8A at a magnification level of approximately 5000 times.Only the Ag coated dielectric tape layer 30 is visible. Pockets of Agmetal 605 formed within the dielectric tape layer 30 are also visible.As noted above, the pockets 605 of metal (e.g., Ag) in this exemplarysecond sample MLCC 100-2 (and the first exemplary sample MLCC 100-1)having longer soak times are larger in size relative to the pockets 605of the third and fourth sample MLCCs 100-3, 100-4 having longer soaktimes but are less frequent in number.

FIGS. 9A-9D illustrate cross-sectional views produced by an opticalmicroscope of other second samples corresponding to the second sampleMLCC 100-2 (LT-3088B) illustrated in FIGS. 8A-8C. Specifically, FIGS.9A-9C illustrate an optical microscope cross-sectional view of secondsample MLCC 100-2 at a magnification level of approximately 100 times.In FIGS. 9A-9C, several layers, including the Ag electrode layer 10; Agcoated dielectric tape (30); and un-coated, standard/regular dielectrictape (70) are visible. (The pockets or inclusions of metal 605 are notvisible.) FIG. 9A illustrates a first embodiment of a second sample MLCC100-2 while FIG. 9B illustrates a second embodiment of a second sampleMLCC 100-2 and FIG. 9C illustrates a third embodiment of a second sampleMLCC 100-2, where each embodiment was manufactured in the same batch orset of MLCCs 100.

FIG. 9D illustrates an optical microscope cross-sectional view of asecond sample MLCC 100-2 (LT-3088B) at a magnification level ofapproximately 1000 times. In this FIG. 9D, several layers including Agelectrode layers 10, dielectric layers 20A, and Ag coated dielectrictape layer 30 are present. Pockets of Ag metal 605 are also visible.

FIGS. 10A-10C illustrate cross-sectional views produced by a scanningelectron microscope (SEM) of a third sample MLCC 100-3 (LT-3088A) usingAg coated dielectric tapes 30 after sintering the MLCC 100-3 atapproximately 975 C for approximately one hour of soaking Morespecifically, FIG. 10A illustrates a SEM cross-sectional view of thethird sample MLCC 100-3 at a magnification level of approximately 500times. Several instances of the layers, including Ag electrode layers10, dielectric layers 20A, and Ag coated dielectric tape layer 30 arepresent. Pockets of Ag metal 605 are also visible.

FIG. 10B illustrates a SEM cross-sectional view of the third sample MLCC100-3 of FIG. 10A at a magnification level of approximately 2000 times.Several instances of the layers (but fewer than those illustrated inFIG. 10A) are visible, including Ag electrode layers 10, dielectriclayers 20A, and Ag coated dielectric tape layer 30 are present. Pocketsof Ag metal 605 are also visible.

FIG. 10C illustrates a SEM cross-sectional view of the third sample MLCC100-3 of FIG. 10A at a magnification level of approximately 5000 times.Only the Ag coated dielectric tape layer 30 is visible. Pockets of Agmetal 605 formed within the dielectric tape layer 30 are also visible.As noted above, the pockets of Ag metal 605 appear much more frequent inthis faster soaking sintering third sample MLCC 100-3 (and fourth sample100-4), but are smaller in size relative to the slower soaking first andsecond sample MLCC 100-1, 100-2.

FIGS. 11A-11D illustrate cross-sectional views produced by an opticalmicroscope of other third samples corresponding to the third sample MLCC100-3 (LT-3088A) illustrated in FIGS. 10A-10C. Specifically, FIGS.11A-11C illustrate an optical microscope cross-sectional view of a thirdsample MLCC 100-3 at a magnification level of approximately 100 times.In FIG. 11A, several layers, including the Ag electrode layer 10; Agcoated dielectric tape (30); and un-coated, standard/regular dielectrictape (70) are visible. (The pockets or inclusions of metal 605 are notvisible.) FIG. 11A illustrates a first embodiment of third sample MLCC100-3 while FIG. 11B illustrates a second embodiment of a third sampleMLCC 100-3 and FIG. 11C illustrates a third embodiment of a third sampleMLCC 100-3, where each embodiment was manufactured in the same batch orset of MLCCs 100.

FIG. 11D illustrates an optical microscope cross-sectional view of athird sample MLCC 100-3 at a magnification level of approximately 1000times. In this FIG. 11D, several layers including Ag electrode layers10, dielectric layers 20A, and Ag coated dielectric tape layer 30 arepresent. Pockets of Ag metal 605 are also visible.

FIGS. 12A-12C illustrate cross-sectional views of a fourth sample MLCC100-4 using Ag coated dielectric tapes produced by a scanning electronmicroscope (SEM) after sintering the MLCC at approximately 975 C forapproximately one hour of soaking More specifically, FIG. 12Aillustrates a SEM cross-sectional view of the fourth sample MLCC 100-4at a magnification level of approximately 500 times. Several instancesof the layers, including Ag electrode layers 10, dielectric layers 20A,and Ag coated dielectric tape layer 30 are present. Pockets of Ag metal605 are also visible.

FIG. 12B illustrates a SEM cross-sectional view of the fourth sampleMLCC 100-4 (LT-3088B) of FIG. 12A at a magnification level ofapproximately 2000 times. Several instances of the layers (but fewerthan those illustrated in FIG. 12A) are visible, including Ag electrodelayers 10, dielectric layers 20A, and Ag coated dielectric tape layer 30are present. Pockets of Ag metal 605 are also visible.

FIG. 12C illustrates a SEM cross-sectional view of the fourth MLCC 100-4sample of FIG. 12A at a magnification level of approximately 5000 times.Only the Ag coated dielectric tape layer 30 is visible. Pockets of Agmetal 605 formed within the dielectric tape layer 30 are also visible.As noted above, the pockets of Ag metal 605 appear much more frequent inthis faster soaking sintering fourth sample MLCC 100-4 (and third sample100-3), but are smaller in size relative to the slower soaking first andsecond sample MLCC 100-1, 100-2

FIGS. 13A-13D illustrate cross-sectional views produced by an opticalmicroscope of other fourth samples corresponding to the fourth sampleMLCC 100-4 (LT-3088A) illustrated in FIGS. 12A-12C. Specifically, FIGS.13A-13C illustrate an optical microscope cross-sectional view of afourth sample MLCC 100-4 at a magnification level of approximately 100times. In FIGS. 13A-13C, several layers, including the Ag electrodelayer 10; Ag coated dielectric tape (30); and un-coated,standard/regular dielectric tape (70) are visible. (The pockets orinclusions of metal 605 are not visible.) FIG. 13A illustrates a firstembodiment of a fourth sample MLCC 100-4 while FIG. 13B illustrates asecond embodiment of a fourth sample MLCC 100-4 and FIG. 13C illustratesa third embodiment of a fourth sample MLCC 100-4, where each embodimentwas manufactured in the same batch or set of MLCCs 100.

FIG. 13D illustrates an optical microscope cross-sectional view of afourth sample MLCC 100-4 at a magnification level of approximately 1000times. In this FIG. 13D, several layers including Ag electrode layers10, dielectric layers 20A, and Ag coated dielectric tape layer 30 arepresent. Pockets of Ag metal 605 are also visible.

Modified Manufacturing Process Coupled with Unique Component Selectionfor Constructing the 3-D Capacitors of FIGS. 14-22: Metal Coated CeramicParticles

By using metal coated ceramic particles in place of the exemplarynon-coated ceramic powder 205 described above, the modified ceramiccapacitor manufacturing method 101 may also be used to createthree-dimensional capacitor embodiments.

Metal-coated ceramic powders featuring a continuous particulate coatingsuch as, but not limited to, silver coated dielectrics are utilized invarious embodiments of a three-dimensional MLCC. Silver coated glassbeads are available as of this writing from Technic, Inc. of Woonsocket,R.I. and Potters Industries, Inc. of Malvern, Pa.

Typically, the metal coating of the metal-coated ceramic powder isconsistent with the conductive powder that may be used to create anelectrode layer such as, but not limited to, silver or silver-palladiumalloy in the case of a precious metal MLCC and nickel or nickel alloysin the case of a base metal MLCC. In other embodiments, metal-coatedceramic powders having inconsistent, defective coatings can be employed.Moreover, although the particulate coating is substantially consistentin some metal-coated ceramic powders prior to the powder beingincorporated into a given three-dimensional capacitor embodiment,defects in the continuity of the coating may occur during the process ofmixing the metal coated ceramic particulates into pastes. Regardless ofwhether a coated particulate features a continuous, consistent coatingor an inconsistent, defective coating, a coated particulate may be usedto effectively form a dielectric layer of a three-dimensional capacitorembodiment.

Advantageously, because of the inherent surface tension between themetal coating and ceramic particulate substrate, discontinuity of themetal coating may occur as a result of exposure to a sinteringtemperature. One of ordinary skill in the art will understand thatexposure of a metal-coated particulate to a given sintering temperaturemay cause the metal coating to flow from the particulate and aggregatein voids between neighboring particulate. The resulting aggregations ofmetal coating that has flowed from the surface of a dielectricparticulate may settle into cavities between juxtaposed dielectricparticulate and simultaneously contact an anode or cathode layer withinthe MLCC, thereby effectively creating a conductive extension of theanode or cathode layer that protrudes substantially perpendicularly fromthe electrode layer into the dielectric layer. Notably, andadvantageously, multiple protrusions of aggregated metal coating serveto increase the capacitive density of the MLCC, without expanding theoverall space footprint of the MLCC, by virtue of increasing the surfacearea attributable to the conductive layers. The thickness of theprotrusion that may result from some aggregations of the metal coatings,after sintering, is believed to be between 1% and 90% of an overallparticle thickness that ranges between about 0.001 microns and about 10microns.

One of ordinary skill in the art will recognize that variousmanufacturing and material parameters can be leveraged to control theflow and aggregation of a conductive coating from a coated dielectricparticulate and, therefore, even though particular process parametersetting combinations or material features may be novel, or render novelresults, variations in process parameter settings or material featureswill not limit the scope of the present disclosure. Manufacturingparameters and material features that may be leveraged to affect theflow and aggregation of metal coating from metal-coated particulateinclude, but are not limited to, the metal coating percentage, thethickness of the dielectric layer, sintering temperature and sinteringtime.

Some embodiments of a three-dimensional capacitor may leveragedielectric material selection composed of core-shell ceramic particles.In some embodiments, the core in a core-shell ceramic particle may havethe composition of BaTiO3 while the shells may be rich in dopants tomodify the temperature coefficients of the capacitance. The compositiondistribution (core-shell structure) may provide a consistent dielectricconstant over the required temperature range.

FIG. 14 illustrates a cross-sectional view of a single EDE tri-layer 300that may form one exemplary embodiment of a three-dimensional capacitor,wherein three-dimensional structures (protrusions) in the form of metalaggregates (inclusions) are formed from conductive coatings ondielectric particulates. The dielectric layer 305 may comprise, forexample, metal coated ceramic particles 315, wherein the conductivemetal coating on the ceramic particulate may include, but is not limitedto, silver-palladium alloys, palladium, palladium alloys, platinum,platinum alloys, silver, silver alloys, gold, gold alloys, etc. In someimplementations of the EDE tri-layer 300 the volume fraction of themetal with the dielectric layer can be, e.g., at least about 10%, or atleast about 20%, or at least about 30%, or at least about 40%, e.g., ina range of about 40% to about 60%. As a non-limiting example ofembodiments that may include silver-palladium coating on dielectricparticulate, the percent by weight composition of the silver-palladiumcoating may be in the range of about 95% Ag and about 5% Pd, morepreferably about 90% Ag and about 10% Pd, and most preferably about 70%Ag and about 30% Pd.

The conductive metal coating on dielectric particulate used in someembodiments may include other precious metals and their respectivealloys such as, but not limited to, iridium, Rhodium, and ruthenium.Additionally, some embodiments may include a particulate with a metalcoating containing base metals such as, but not limited to, copper,nickel, iron, cobalt, manganese, titanium, zinc. Further, it isenvisioned that still other embodiments may include dielectricparticulate coated with refractory metals such as, but not limited to,tungsten, molybdenum, zirconium, tantalum, and niobium.

Moreover, although the exemplary dielectric layer 305 is described ascomprising coated ceramic particles, it is also envisioned that thedielectric portion of coated particles in layer 305 may comprisedielectric matter other than ceramics such as, but not limited to,ceramic and glass-ceramic, precious metal coated ceramics such as, butnot limited to, silver-coated ceramics, palladium-coated ceramics,silver palladium coated ceramics, etc. as well as silver coatedformulated barium titanate based dielectrics, silver coated glass beads,and inorganic oxides such as, but not limited to, alumina and tantalumoxide. Also, while the metal coating 320 on the ceramic particles 315may be substantially uniform (not shown) prior to creation of adielectric green sheet, the metal coating 320 advantageously becomesdiscontinuous after sintering.

Dielectric layer 305 is depicted as the entire layer of ceramicparticles 315 positioned between two electrode plates 310A, 310C.Notably, while plate 310A has been designated in the FIG. 14illustration as representing the anode plate, and plate 310C as thecathode plate, one of ordinary skill in the art will understand thateither conductive plate 310 could perform as the anode or the cathode ina charged capacitor, as an application may require. The ceramicparticles of dielectric layer 305 typically range in size from about0.01 to about 10 microns, but other dielectric particle size ranges arepossible as understood by one of ordinary skill in the art.

As explained above, the discontinuity in the metal coating 320 aftersintering of the ceramic chips is mainly due to the surface tensionbetween the dissimilar materials of the coated dielectric particles 315,such as, but not limited to, metal and ceramic. Generally, aftersintering temperature is reached, the temperature causes the metalcoating 320 to flow and aggregate into cavities 325 between thedielectric ceramic particles 315. Advantageously, the aggregated metal320 that results from the melted particulate coating will cool to form aplurality of three-dimensional structures or protrusions 320 extendingor protruding substantially perpendicular down through the dielectriclayer from either the anode 310A or cathode 310C plates. Many of thethree-dimensional structures 320, which comprise conductive material,may form an interface structure 330 with either the anode 310A orcathode 310C plate of the EDE tri-layer 300. One of ordinary skill inthe art will understand that the overall surface areas attributable tothe conductive plates 310A, 310C may be effectively increased, withdielectric material dispersed all between the dielectric particles 315,thus increasing the overall capacitive density of the capacitor 300.

As a non-limiting example of capacitive density increase, embodiments ofa three-dimensional capacitor have been estimated to have an increasedcapacity density of anywhere from about ten (10) times to about onethousand (1000) times over traditional capacitor designs. Even so, theabove range of capacity density increase is offered for exemplarypurposes only and will not be a limiting factor on the scope of thedisclosure. One of ordinary skill in the art will recognize that a giventhree-dimensional capacitor embodiment may advantageously have anincreased capacity density when compared to other capacity designs thatrequire an equivalent, or nearly equivalent, space footprint in acircuit.

Importantly, one of ordinary skill in the art will understand thatangles besides those which are substantially perpendicular to thedielectric 305 and conductive 310 layers are envisioned as a result ofthe aggregation of the dielectric particulate coating 315 and, as such,the above description of the three-dimensional structures 330 beingsubstantially perpendicular to the various layers will not limit thescope of a three-dimensional capacitor 300. The three-dimensionalstructures 315, 320 that are formed both increase the overall surfacearea attributable to a given conductor plate and also essentially form aplurality of small micro-capacitor tri-layer arrangements within a givenEDE tri-layer 300.

Metal-coated ceramic powders suitable for use in the dielectric layer305 in order to create a three-dimensional capacitor 315, such as theexemplary embodiment described above, can be produced commercially. Theinnovative capacitor structure may include various dielectricparticulate materials and coating combinations, although certaincombinations may be more advantageous than others. Moreover, one ofordinary skill in the art will recognize that various parameters may beused to control aspects or properties of the three-dimensionalstructures in a three-dimensional capacitor such as, but not limited to,the selection of metal coating percentage, sintering temperature, andsintering time.

FIG. 15 illustrates a cross-sectional view of a single EDE layer 400that forms one exemplary embodiment of a three-dimensional capacitor,wherein three-dimensional structures are formed from metal particles 421mixed into the dielectric slurry of dielectric particles or coateddielectric particles. Consistent with step 120 of method 101 describedabove, the electrode plates 410A, 410C are printed over the green tape215, 405, wherein the green tape 215, 405, instead of being made from apure dielectric slurry 210, is made of a mixture of metal particulate421 and dielectric particles or metal coated dielectric particulate 415.As described above relative to the FIG. 14 embodiment, it is envisionedthat the metal coated dielectric particulate may be comprise anycombination of conductive coating and dielectric particulate and, assuch, it will be understood that specific particulate and conductivecoating material choices and combinations are offered herein forillustrative purposes and will not limit the scope of the disclosure.Similarly, it is envisioned that metal particulate 421 may comprise anysuitable conductive material including, but not limited to, silver,silver palladium alloy, nickel, nickel alloys, copper, copper alloys,etc. The metal coating of the dielectric particles 415 may bediscontinuous as a result from the mechanical mixing with the metalparticulate 421, however, after sintering, the coating will generallyflow and aggregate such that three-dimensional structures or protrusions420 are formed substantially perpendicular to the dielectric layer, someforming on interface 430A with the top electrode and some forming oninterface 430B and being connected to the bottom electrode, with metalparticulate 421 aggregated throughout.

The manufacturing of the three-dimensional capacitor layer illustratedin FIG. 14 is essentially equivalent to that which was describedrelative to method 101. Again, to manufacture the three-dimensionalcapacitor of the exemplary embodiment illustrated in FIG. 14,modifications to the manufacturing process as described in connectionwith FIGS. 1-2 are usually made. Specifically, in step 105, if a metalcoated dielectric 315 is used in place of the ceramic dielectric powder205 in the MLCC production, the resulting three-dimensional capacitorwill have structure similar to the FIG. 14 embodiment. Similarly, if themechanical mixture of conductive particulate 421 and dielectricparticles or coated dielectric particulate 415 is inserted in place ofpowder 205, the resultant three-dimensional capacitor will havestructure similar to the FIG. 15 embodiment.

Unique Component Selection and Additional Manufacturing Steps

By incorporation of additional manufacturing steps to accommodatevarious novel component selections, a unique ceramic capacitormanufacturing method 101 may be used to create three-dimensionalcapacitors.

FIG. 16 illustrates a cross-sectional view of a single EDE tri-layer 500that may form an exemplary embodiment of a three-dimensional capacitor,wherein metal particles 521 are impregnated into the dielectric greentape 215, 505. A metal powder containing fine particulate may be madeinto a slurry and applied to the surface of the dielectric green tape215 described relative to method 101 such that the metal particles 521are forced into voids between the dielectric particles 515. Similar tothat which has been described relative to the FIG. 14 and FIG. 15embodiments, it is envisioned that metal particulate 521 may compriseany suitable conductive material including, but not limited to, silver,silver palladium alloy, nickel, nickel alloys, copper, copper alloys,etc. As such, it will be understood that metal particulate materialchoices will occur to those with ordinary skill in the art and will notlimit the scope of the disclosure.

Essentially, the application of the fine particle metal slurry causesthe metal particles 521 to penetrate the “pores” of the dielectric tape215, 505, thereby potentially aggregating to create protrusions 522 thatform an interface 530 with plates 510A, 510C. Advantageously, anyinterfaced protrusions 522 may operate to effectively increase thesurface area that is attributable to conductive plates 510A, 510C.

Referring back to method 101, an additional step may be added after step110, and before screen printing step 120, such that the deposition of aslurry containing suitably fine-sized metal particulate 521 can beapplied to the dielectric tape 215 before printing the electrode ink510A, 510B in the electrode screen printing step 120.

FIG. 17 illustrates a cross-sectional view of a single EDE tri-layer 600that may form an exemplary embodiment of a three-dimensional capacitor,wherein metal particles 621 are impregnated into the dielectric greentape 215, 605 and the conductor plates comprise a layer of low meltingpoint electrode material adjacent to the dielectric layer 605. Similarto the FIG. 16 embodiment, FIG. 17 illustrates an electrode structureformed by diffusion of a low melt point metal conductor 611A, 611Cadjacent to the dielectric layer 605 (low melt point is relative to themelt point of the material used for the primary conductor plates 610A,610C). For example, use of a 100% silver electrode 611A, 611C beneath anupper electrode layer 610A, 610C of about 95% Ag/5% Pd (silver/palladiumalloy) may increase the metal flow into cavities between dielectricparticulate 615 during sintering step 140, thereby creatingthree-dimensional structures or protrusions 622 in conjunction withoptional impregnated metal particulate 621. Notably, while the FIG. 17illustration depicts an embodiment comprising both low melt pointconductor layers 611A, 611C and impregnated metal particulate 621, itwill be understood that similar embodiments may not comprise theimpregnated particulate 621 as the low melt point material may suitablygenerate conductive protrusions as it flows upon sintering into voidsbetween the dielectric particulate 615.

Similar to that which has been described relative to the FIG. 14 andFIG. 15 embodiments, it is envisioned that metal particulate 621 maycomprise any suitable conductive material including, but not limited to,silver, silver palladium alloy, nickel, nickel alloys, copper, copperalloys, etc. As such, it will be understood that metal particulatematerial choices will occur to those with ordinary skill in the art andwill not limit the scope of the disclosure. Importantly, one of ordinaryskill in the art will also recognize that similar embodiments to theexemplary FIG. 17 embodiment may call for the low melt point conductorlayers to be positioned above the primary conductors such that theprimary conductors are juxtaposed to the dielectric.

Referring back to method 101, an additional step may be added withinscreen printing step 120, such that the low melting electrode paste isprinted in the same step but prior to the printing of the primaryelectrodes 610.

The exemplary embodiments of a three-dimensional capacitor, which havebeen described and depicted relative to FIGS. 3 through 6, utilizeelectrode layers comprising primarily conductive particulate or rigidplates such as, but not limited to, silver, silver/palladium alloy,nickel, nickel alloys, copper or copper alloys. Other embodiments of athree-dimensional capacitor, however, utilize anode and cathode layerscomprising metal coated, nonconductive material such as, but not limitedto, silver coated ceramic particulate or any combination of conductivecoating and nonconductive material. Moreover, in such embodiments thatutilize metal coated, non conductive material for the conductive layersof a three-dimensional capacitor, the specific percent by weight in theconductive layer that is attributable to the nonconductive material or,alternatively, the conductive coating, may vary by embodiment and canrange from about 1% to about 90%. Advantageously, such embodiments mayrealize a cost savings over traditional capacitor arrangements inaddition to providing various benefits of three-dimensional structure.

FIG. 18 illustrates a cross-sectional view of a single EDE tri-layer 700that may form an exemplary embodiment of a three-dimensional capacitor,wherein metal coated particulate 720 is used to create the conductivelayers 710A, 710C between which a dielectric layer 705 is sandwiched. Inthe exemplary FIG. 7 embodiment, electrode ink 225 applied over thegreen tape 705 at screen printing step 120 may comprise conductivecoated particulate, such as, but not limited to, metal coated ceramicpowder as well as any other particulate and coating combinations thatmay occur to one of ordinary skill in the art. Advantageously, uponexposure to sintering temperatures at step 140, a functional electrodelayer 710 is formed from the ink when a three-dimensional metal network720 results from the aggregation of the melted particulate coating inthe electrode layers 710. Importantly, in some embodiments, thethree-dimensional metal network 720 in the electrode layers 710 may alsobe achieved by mechanically mixing the electrode and dielectric.

FIG. 19 illustrates a cross-sectional view of a single EDE tri-layer 800that may form an exemplary embodiment of a three-dimensional capacitor,wherein a metal coated ceramic layer 811A, 811C is formed between thedielectric layer 805 and the electrode layers 810A, 810C. The dielectriclayer 805 in this exemplary embodiment may be formed from dielectricmaterials, such as, for example, standard uncoated ceramics. Themetal-coated ceramic layer 811 forms a network 820 and is electricallyconnected to the respective electrode layers 810. Similar to the lowmelt point conductive layer described relative to the FIG. 17 embodimentof a three-dimensional capacitor, the metal-coated ceramic layers 811can be printed at step 120 using ink containing metal-coated ceramicparticles, prior to printing the standard electrodes 810A, 810C(alternatively, the standard electrode layer could be printed prior tothe metal coated ceramic particulate layer in some embodiments).

The exemplary embodiments of a three-dimensional capacitor which havebeen described and depicted in FIGS. 3 through 8, are embodiments formedfrom the controlled flow of conductive coatings on dielectricparticulate and/or impregnation of conductive particles.

Manufacturing Process with Mechanical Conversion Steps and/orPre-Designed Plate Geometry

Some embodiments of a three-dimensional capacitor have three-dimensionalstructures positioned substantially perpendicular to the dielectriclayer by virtue of planned conductor/dielectric geometry and/ormechanical conversion techniques.

FIG. 20 illustrates a cross-sectional view of a single EDE tri-layer 900that may form an exemplary embodiment of a three-dimensional capacitor,wherein three-dimensional structures (or protrusions) 920 protrudeperpendicularly from the anode 910A and cathode 910C layers into thedielectric 905. Two electrodes 910 are separated by a dielectric layer905. The dielectric layer 905 in the exemplary FIG. 20 embodiment may beformed from conventional dielectric materials, such as, but not limitedto, standard uncoated ceramics, however it is envisioned that coatedparticulate similar to that which is described above may be used invarious embodiments.

The “slots” or “bores” that accommodate the electrode protrusions 920are created in dielectric 905 by any suitable mechanical device orboring method as understood by one of ordinary skill in the art.Substantially perpendicular, three-dimensional electrode extensions orfinger-like protrusions 920 are then created by filling the slots withconductive material. Connected to their respective electrodes 910A,910C, electrode protrusions 920 create additional capacitor arrangementswithin the main capacitor 900 at areas of overlap 921 between anode andcathode protrusion 920 pairs. Consistent with embodiments describedabove, the electrode extensions 920 work in conjunction with the primaryelectrode plates 910 to increase the effective surface area of theelectrode layers and thusly improve the capacitive density of acapacitor that includes such a tri-layer 900.

In FIG. 20, the slots and corresponding electrode protrusions 920 aredepicted as being perpendicular to the cross section. It should beunderstood, however, that the protrusions 920 can be parallel to thecross section to provide for electrode extensions 920 that areelectrically connected to one of the primary conductor plates by virtueof edge metallization and termination techniques, even though such alayout is not shown. Suitable ways to create the slots may include, butare not limited to, laser drilling, mechanical punching, etc. Suitableways to fill the slots to create electrode protrusions may include, butare not limited to, printing electrode ink over the dielectric tape tofill the slots or printing the dielectric ink to fill altering slots inorder to insulate a given electrode 920 from a given conductor layer910. It is envisioned that the patterning can also be accomplished viaphotolithographic techniques or imprint printing. Other methods forleveraging bores in the dielectric in order to generate athree-dimensional capacitor embodiment will occur to those with ordinaryskill in the art and, as such, the particular exemplary embodimentsdepicted in the figures, and described herein, will not limit the scopeof the disclosure as understood to one of ordinary skill in the art.

With regards to the exemplary embodiment depicted in FIG. 20, andsimilar embodiments, it should be apparent to one of ordinary skill thatthe pattern density, therefore, the capacitance, is limited by theresolution of the mechanical means to form the slots and the printingmeans to fill the slots.

FIG. 21 illustrates a cross-sectional view of a single EDE tri-layer1000 that may form an exemplary embodiment of a three-dimensionalcapacitor, wherein three-dimensional structures (or protrusions) 1020protrude from the primary conductor layers into the dielectric layer1005. Similar to previously described embodiments, the exemplaryembodiment of FIG. 21 advantageously increases capacitive density viathe increase of anode and cathode surface area that is coupled to thedielectric 1005. The electrode structures 1020 may be formed bypatterning techniques such as, but not limited to, imprint printing,molding, etc. That is, the three-dimensional structures 1020 may becreated in a modified green tape component via application (such asstamping) of a die with teeth to the dielectric green tape 215 prior toscreen-printing the electrode layer 1010 at step 120 of exemplary method101.

The dielectric layer 1005 in the exemplary FIG. 21 embodiment may beformed from conventional dielectric materials, such as standard uncoatedceramics, but such is not required in all embodiments. Upon screenprinting the modified green tape, the electrodes 1010 acquireprojections 1020 that are attributable to the exemplary teeth imprintsthat resulted from stamping or molding the green tape into the modifieddielectric layer 1005. The projections 1020 may function as extendedelectrodes to effectively create additional surface area within the maincapacitor 1000 for gathering electrical charge.

For manufacturing the exemplary embodiment of FIG. 21, and similarembodiments, modifications to the manufacturing method 101 may includeadding texture to the dielectric tape after or during the “tape casting”step 110. Notably, one of ordinary skill will recognize that patternsfor the projections 1020 other than those illustrated can be used insimilar embodiments of a three-dimensional capacitor.

Referring now to FIG. 22 illustrates a cross-sectional view of anotherexemplary embodiment of a three-dimensional capacitor 2200 having aplurality of discrete metal inclusions 320 in the dielectric layer 305but without a “depletion layer” adjacent to the electrodes. Thisexemplary embodiment is similar to the exemplary embodiment illustratedin FIG. 14, so only the differences will be described below. Accordingto this exemplary embodiment, there are three dielectric layers 305.These three dielectric layers 305 are positioned adjacent to each otherwithout any depletion layer disposed between them. A depletion layer 705or 805 may be found in the exemplary embodiments of FIGS. 18-19. Adepletion layer 705, 805 is one that is a substantially metal freedielectric layer.

Certain steps in the processes or process flow described in thisspecification must naturally precede others for a giventhree-dimensional capacitor embodiment to function as described.However, the manufacture of a three-dimensional capacitor is not limitedto the order of the steps described if such order or sequence does notalter the functionality of the three-dimensional capacitor resultingthere from. That is, it is recognized that some steps may be performedbefore, after, or in parallel with other steps without departing fromthe scope and spirit of the disclosure. In some instances, certain stepscan be deleted or not performed, without departing from the invention.

The three-dimensional capacitor as described above may comprise about 1to about 1000 layers, preferably about 300 to about 500 layers, withdielectric layer thicknesses often being from about 1 to about 50microns. When only a single layer of dielectric is utilized, a singlelayer capacitor is formed, often seen in the passive integration in lowtemperature co-fired ceramic (LTCC) technologies. The three-dimensionalcapacitor may also comprise as small as a 0402 size (about 0.04 inch byabout 0.02 inch) and even a 0201 size (about 0.02 inch by about 0.01inch).

CONCLUSIONS

Accordingly, the method 101, exemplary embodiments, and actual samplesdescribed above disclose capacitors that may include a pair ofelectrodes (such as 10 in FIG. 1D, and 310A, 310C in FIG. 14). Ametalized dielectric layer, formed from metal coated dielectric tapes(such as 30 in FIG. 1C, generally found in FIGS. 1C-13) or metal coatedceramic particles, (such as 315 of FIG. 14, generally found in FIGS.14-22) may be disposed between the pair of electrodes. The metalizeddielectric layer may comprise a plurality of metal aggregates (such asmetal pockets 605 of FIGS. 1C and 6, such as metal coatings 320 of FIG.14, such as metal particles 421 of FIG. 15, etc.) distributed within adielectric material (such as 30 of FIG. 1 and FIG. 6, such as ceramicparticles 320 of FIG. 14, such as dielectric particles 415 of FIG. 15)such that a volume fraction of metal in the metalized dielectric layeris at least about 30%. The plurality of metal aggregates may beseparated from one another by the dielectric material.

The capacitor may include least one substantially metal free dielectriclayer referred to as a “depletion layer”, such as 20A in FIG. 1C, thatseparates the metalized dielectric layer (30 of FIG. 1C,) from at leastone of the electrodes (10 of FIG. 1C). The volume fraction of the metalmay be in a range of about 30% to about 60%, and more preferably, thevolume fraction of the metal is in a range of about 40% to about 60%.

The metalized dielectric layer may have a thickness in a range of about0.01 micron to about 50.0 microns. The resultant capacitor describedabove may exhibit a capacitance which is at least five times of thatwithout the metalized dielectric layer. As noted above, the dielectricmaterials in the capacitor may comprise a ceramic. The ceramic maycomprise any one of a barium titanate based ceramics or other type ofcapacitor dielectrics, such as, lead magnesium tantalates and niobates,a glass ceramic, inorganic oxides, alumina oxide, and tantalum oxide.

As noted above, the ceramic may comprise a plurality of ceramicparticles (such as particles 315 of FIG. 14) that are partially coatedwith metal aggregates (coatings 320 as illustrated in FIG. 14). Theceramic particles may have a size in a range of about 0.001 microns toabout 10 microns.

The metal aggregates used may comprise any one of silver, palladium,nickel, gold, platinum, iridium, tungsten, molybdenum, tantalum,niobium, hafnium, rhenium, nickel, and copper. The metal aggregates andat least one of the electrodes may or may not have at least one metallicconstituent in common. That is, the metal aggregates and at least one ofthe electrodes may not be formed of the same metal. The electrodes maybe formed of any of silver, palladium, nickel, gold, platinum, iridium,tungsten, molybdenum, tantalum, niobium, hafnium, rhenium, nickel, andcopper.

A MLCC formed by the techniques described above may include a pluralityof electrodes and a plurality of dielectric layers, in which eachdielectric layers is disposed between two of the electrodes. At leastone of the dielectric layers of the MLCC has a metalized portioncomprising a dielectric material in which a plurality of metalinclusions are distributed. A volume fraction of metal in the metalizedportion is at least about 20%, and more particularly, at least about 30%and wherein said the inclusions are separated from another by thedielectric material.

A metalized portion of the dielectric layer may comprise a mixture of aceramic and a plurality of metal inclusions. The ceramic may comprise aplurality of ceramic particles. The ceramic particles may have sizes ina range of about 0.001 microns to about 10 microns.

The metal inclusions and at least one of the electrodes of the capacitormay or may not have at least one metal constituent in common. The metalinclusions and the at least one electrode may or may not be formed ofthe same metal. The metal inclusions may comprise silver, anon-oxidizing metal. The dielectric layer may comprise a substantiallytwo-phase composition that includes a metal coated dielectric tape orceramic particles coated with a metal.

A capacitor produced by the techniques described above may include apair of electrodes 10 and a dielectric layer 30,40 disposed between thepair of electrodes 10 as illustrated in FIG. 1C. The dielectric layer30,40 may comprise at least one metalized portion 30 having a pluralityof discrete metal inclusions 605 and at least one substantially metalfree portion 20A separating said at least one metalized portion 30 fromat least one of the pair of electrodes 10 as illustrated in FIG. 1C. Thein-situ formed depletion layer 20A may have a thickness of about 0.1micron to 10 microns.

A method of forming a metal-dielectric composite is disclosed whichincludes (A) coating a plurality of dielectric particles with a metal toform a plurality of metal-coated dielectric particles (applying a metalcoating to a dielectric tape as illustrated as FIGS. 1C-13 OR coatingparticles individually as illustrated in FIGS. 14-22)); and sinteringthe plurality of metal-coated dielectric particles at a temperature ofat least about 750° C. to 950° C. for silver to transform said metalcoatings into a plurality of discrete, separated metal aggregates.

The method includes selecting the sintering temperature to be in a rangeof about 750° C. to about 950° C. if silver is used. The plurality ofmetal-coated dielectric particles are usually sintered for a duration ina range of about 0.1 to 10 hours. As noted above, in the method andsystem, the plurality of dielectric particles or dielectric tapecomprises a ceramic material. The dielectric particles may have sizes ina range of about 0.001 microns to about 10 microns. Meanwhile, the metalapplied to the dielectric particles may comprise any of silver,palladium, nickel, gold, platinum, iridium, tungsten, molybdenum,tantalum, niobium, hafnium, rhenium, nickel, and copper. The metal maybe substantially non-oxidizing.

The exemplary three-dimensional capacitor embodiments described aboveemploy a so-called ‘tape process’ (as shown in FIGS. 1A-1B). It isenvisioned, however, that three-dimensional capacitor embodiments canalso be made using the so-called ‘wet process’, in which the dielectriclayer is actually printed using dielectric slurry.

A three-dimensional capacitor and methods of its manufacture have beendescribed using detailed descriptions of embodiments thereof that areprovided by way of example and are not intended to limit the scope ofthe disclosure. The described embodiments comprise different features,not all of which are required in all embodiments of a three-dimensionalcapacitor. Some embodiments of a three-dimensional capacitor utilizeonly some of the features or possible combinations of the features.Variations of embodiments of a three-dimensional capacitor and methodsof its manufacture are included within the scope of the invention asunderstood to one of ordinary skill in the art.

It is envisioned that the systems, devices, methods and arrangements, orfeatures or aspects thereof, disclosed herein in the context of MLCCscan be used in other related or analogous applications such as, but notlimited to, ceramic and plastic polymer substrates for embedded passivecomponent applications. Thus, one of ordinary skill in the art willrecognize that disclosed embodiments, or variations thereof, can beincorporated into, among other applications, low-temperature co-firedceramic (LTCC) applications, high-temperature co-fired ceramic (HTCC)applications, thick film hybrid circuits and printed circuit boards(PCB). Further, it is envisioned that disclosed embodiments, orvariations thereof, can be employed in super-capacitors orsuper-capacitor applications, as electrode protrusions in athree-dimensional capacitor advantageously generate an increase inelectrode surface area that may be desirable in super-conductors orsuper-conductor applications.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Therefore, although selected aspects have been illustrated and describedin detail, it will be understood that various substitutions andalterations may be made therein without departing from the spirit andscope of the present invention, as defined by the following claims.

What is claimed is:
 1. A capacitor, comprising: a pair of electrodes; ametalized dielectric layer disposed between said pair of electrodes,said metalized dielectric layer including a plurality of metalaggregates distributed within a dielectric material and wherein saidplurality of metal aggregates are separated from one another by saiddielectric material, the metal aggregates being distributed in anon-uniform and discontinuous manner such that the metal aggregates formprotrusions having dissimilar geometries.
 2. The capacitor of claim 1,further comprising at least one substantially metal free dielectriclayer formed in-situ during sintering and which separates said metalizeddielectric layer from at least one of said electrodes.
 3. The capacitorof claim 1, wherein such that a volume fraction of metal in saidmetalized dielectric layer is in a range of about 30% to about 60%. 4.The capacitor of claim 1, wherein said volume fraction of the metal isin a range of about 40% to about 50%.
 5. The capacitor of claim 1,wherein said metalized dielectric layer is configured as a floatingelectrode.
 6. The capacitor of claim 1, wherein said metalizeddielectric layer is configured as an electrode for electrical couplingwith a voltage terminal.
 7. The capacitor of claim 1, wherein saidmetalized dielectric layer has a thickness in a range of about 0.01micron to about 250.0 microns.
 8. The capacitor of claim 1, wherein saidcapacitor exhibits a capacitive density which is about 2 to about 1000or higher times than that capacitor without the metalized dielectrics.9. The capacitor of claim 1, wherein said dielectric material comprisesa ceramic.
 10. A multi-layer capacitor, comprising: a plurality ofelectrodes; a plurality of dielectric layers, each of said dielectriclayers being disposed between two of said electrodes; at least one ofsaid dielectric layers having a metalized portion comprising adielectric material in which a plurality of metal inclusions aredistributed; and wherein said metal inclusions are separated fromanother by said dielectric material, the metal inclusions beingdistributed in a non-uniform and discontinuous manner such that themetal inclusions form protrusions having dissimilar geometries.
 11. Themulti-layer capacitor of claim 10, further comprising at least onesubstantially metal free dielectric layer formed in-situ duringsintering and which separates said metalized portion from at least oneof said electrodes.
 12. The multi-layer capacitor of claim 10, a volumefraction of metal in said metalized portion is at least about 30%. 13.The multi-layer capacitor of claim 12, wherein said volume fraction ofthe metal is in a range of about 30% to about 60%.
 14. A multi-layercapacitor, comprising: a plurality of electrodes; a plurality ofdielectric layers, each of said dielectric layers being disposed betweentwo of said electrodes; at least one of said dielectric layers having ametalized portion comprising a dielectric material in which a pluralityof metal inclusions are distributed; and wherein said metal inclusionsare separated from another by said dielectric material, the metalinclusions being distributed in a non-uniform and discontinuous mannersuch that the metal inclusions form protrusions having dissimilargeometries, said dielectric material comprises a ceramic.
 15. Themulti-layer capacitor of claim 14, further comprising at least onesubstantially metal free dielectric layer formed in-situ duringsintering and which separates said metalized portion from at least oneof said electrodes.
 16. The multi-layer capacitor of claim 14, a volumefraction of metal in said metalized portion is at least about 30%. 17.The multi-layer capacitor of claim 16, wherein said volume fraction ofthe metal is in a range of about 30% to about 60%.
 18. The multi-layercapacitor of claim 14, wherein said metalized portion is configured as afloating electrode.
 19. The multi-layer capacitor of claim 14, whereinsaid metalized portion is configured as an electrode for electricalcoupling with a voltage terminal.
 20. The multi-layer capacitor of claim14, wherein said metalized dielectric portion has a thickness in a rangeof about 0.01 micron to about 250.0 microns.